What this part is and what it does
The Siemens 3VA1112-1AA36-0KH0 is a SENTRON switch disconnector built in an MCCB-style frame — it looks like a molded-case breaker but carries no overload or short-circuit protection. It's a load-break disconnect rated for 125 A continuous current (Iu) and 690 V AC / 500 V DC maximum operational voltage, with a shunt trip (STL) release for remote opening. The front terminal connection and 3-pole design make it a straight swap-in for panel builders who need a manual disconnect with a trip-alarm signal. The auxiliary contact block carries two auxiliary switches (form C) plus one dedicated trip alarm switch (HQ) — that third contact closes only when the disconnect has opened on a trip signal, so a PLC or annunciator gets a hardwired fault indication without extra wiring.
Duty and ratings
Rated 125 A continuous, 690 V AC — that's full line voltage for most 400 V industrial panels, with headroom for 480 V or 600 V installations. The DC rating of 500 V covers common 400 V DC bus applications. The shunt trip coil is specified for 220-250 V DC or 208-277 V AC, so it works across both common control voltages without a separate power supply. The 2 kA short-time withstand (1 s and 0.5 s) tells you this disconnect is meant to sit behind a current-limiting breaker or fuse — it's not a stand-alone fault interrupter. It's rated for 15,000 mechanical operations, which is typical for a panel disconnect that sees daily switching but not high-cycle automation.
Mounting and integration
Mounts on a DIN rail or panel, 76.2 mm wide (about 4.5 module spaces), 130 mm tall, 70 mm deep. Front terminals accept standard ring or fork lugs — no special busbar adapter required. The IP40 front face keeps dust out of the enclosure but expects a sealed cabinet if washdown is involved. The shunt trip (STL) is wired separately from the main circuit — it draws power only during the trip pulse, so it doesn't add a continuous load to the control transformer. The auxiliary contacts are rated for standard 24 V DC PLC inputs or 120 V AC pilot duty.